This invention relates to the luminaire art and in particular to globes suitable for outdoor luminaires.
The use of transparent or translucent globes to cover or enclose a light fixture used outdoors is well known. Originally such globes were made from glass but recently plastic globes, commonly made from polycarbonate, have come into wide spread use. In recent times, plastic globes have been used in conjunction with light fixtures that have the appearance of old fashioned outdoor fixtures such as street lights. An example of a polycarbonate globe is that manufactured by Hadco, a division of Craftlite, Inc. of Littlestown, Penn. This known globe has a heat reflector mounted in the upper portion thereof above the location for the light bulb. The globe is mounted on a waterproof ballast housing having a removable access lid.
Another example of a known outdoor light fixture that employs a polycarbonate globe is that made by Spring City Electrical Mfg. Co. of Spring City, Penn. Mounted inside this globe is a generally cylindrical glass refractor. A cast aluminum mounting bracket supports this refractor and extends upwardly from the ballast compartment at the bottom of the globe. The use of internal refractors is common in the luminaire art but it suffers from the considerable disadvantage that such refractors do not utilize the light emitted from the bulb in an efficient manner.
A common design for a luminaire used at the top of a post is known as an "Acorn or Type 118" post top luminaire. Up until the present invention, this type of luminaire generally contained I.E.S. type II refractors which put out an I.E.S. type IV medium or long non-cut-off light pattern on the roadway with an average of 15% light utilization on a typical forty foot roadway. Such lighting is considered unacceptable by the latest minimum requirements for roadway lighting. The designation I.E.S. stands for Illuminating Engineers Society. There are five standards set up by this society for patterns for lighting a surface. The type II pattern is considered to be the most desirable for a light fixture located between roadway intersections because it results in the most light being delivered to the lane in which the traffic is moving. On the other hand, at an intersection a type V pattern, which is a circular pattern, is considered to be the most desirable.
A globe constructed in accordance with the present invention can be made to use the available light in a highly efficient manner. In fact, the preferred embodiment of the present invention can use in excess of 80% of the light emitted from the bulb. The globe disclosed herein can be made at a reasonable cost and it can be made to look like an old-fashion globe, if desired.